How can you tell if your cat is clogged?

My car will not boost past 7lbs and it doesn't seem to hit the secondarys very hard. Also the cars smells like its runnig rich. I'm at a loss I have checked all my check valves and all the hoses and still no good. Also the car smokes after I have gotten on it a bit then sit at a light it starts to smoke and it comes up around the doors. I just installed new turbos and downpipe still 7lbs. With the old turbos I was boosting 10-8-11 with crazy oil leaks. WTF is wrong.

 

take it off an visually inspect both ends...

 

Like JSpecRZ said; it will be obvious

Mine died recently, here were my symptoms:

My main cat died a few weeks ago. The only symptom I had was that all of a sudden I went from 11-9-11 to 9-5-7; no matter what I couldn't get more than 7psi. I was on the track at the time and in a span of about 10 minutes the boost kept falling until it stayed at 7psi max.

I pulled the cat and dumped handfulls of brick and wire mesh out of it. Installed another stock cat and the car was perfect again.

No smoke, coughing, sputtering or anything, just less boost.

Imagine a clogged cat like a clog in a drain. As long as there is not too much water coming through there are no problems, but once more tries to pass than the clog can let by, things back up. Since there is less exhaust volume in the primary turbo (less engine rpm) its boost is not affected as much as the secondary turbo (high engine rpm). My results support this as my primary was only 2 psi low with a clogged cat but my secondary was 4 psi low.

 

thanks guys

 

Will a clogged cat will make you exhaust's sound level lower even w/ PFS exhaust? I mean my car is so quiet that a lot of people think is the factory exhaust. Yes I have a boost problem too(8-4-4) with the smoke and the smell too.

 

Check to see how much exhaust you feel coming outta the tail pipe (without getting too close so you don't torch your hand). If it isn't much, then it's prolly clogged. Same thing happened to my f-bird. It got REALLY clogged, so bad in fact that it started to blow back into the motor. Not that the 305's have much power to begin with, it had squat after that.

 

an easy way to check is to disconect the DP/cat flange and place 2 large bolts as spacers inbetween the 2 flanges.
easy on the throtle but see if it passes the point is is cloging at. if it does, you have a bad cat, if nothing, look for other solutions.

 

Very good test!

patfat, did you replace any vacuum lines when replacing the turbos? The fact that you can only get 7 PSI sounds like you don't have the restictor pills installed or a boost controller problem (if you have one).